The invention relates to a fragmentation device and to the method of manufacture, more particularly, to a device for antipersonnel and antimateriel systems which produces fragments of predetermined mass and shape.
Applied research studies conducted a decade ago demonstrated that the fragmentation behavior of a warhead case was affected by a grid system machined or formed on the inner surface of the metal case. When the warhead was detonated, the elements of the grid system acted as dynamic stress raisers and introduced localized regions of high stress concentrations in the case resulting in the initiation of shear fractures in a definite pattern. Once initiated, these fractures propagated along predetermined paths defined by the maximum shear trajectories of the stress field. Feasibility studies regarding the use of inner surface grid systems demonstrated their value in fragmentation warheads, and a production method for producing warhead cases of this type by a hot-cup, cold-draw process was devised. An understanding of the design relationships for use with the method has remained limited, restricted mainly to information obtained from the original studies and to an extrapolation of behavior data based on a quantitative understanding of the response of metals to impulsive loads. The prior art provided for an internal grid structure comprising large diamond grids with symmetrical profile. Fragmentation of steel cases having this structure produces fragments having a variety of shapes and sizes, and the impact pattern is of a nonuniform area coverage. The present invention overcomes this undesirable pattern by providing a device which upon fragmentation produces an impact pattern with a fairly uniform area distribution. The fragments produced are of predetermined mass and shape. Accordingly, it is an object of this invention to provide a means for closer control of fragmentation of impulsively loaded bodies than the means of the prior art .